Cardiac rhythm management system with ultrasound for autocapture or other applications

Abstract

A cardiac rhythm management system provides ultrasound autocapture capability for determining whether a stimulation has evoked a desired response from the heart, and for adjusting an energy of the stimulation based on the observed response from the heart. A first ultrasound element is disposed on a lead in the heart. A second ultrasound element is disposed elsewhere in the heart or in the implanted device. An autocapture determination circuit determines whether motion of the heart chamber indicates a contraction in response to the stimulation, and adjusts the stimulation energy to provide only that energy which is needed to obtain capture. This saves energy, prolonging the life of the implanted device, minimizing the risk and expense to patient associated with early explantation and replacement of the implanted device. Other applications include using ultrasound for (1) determining the strength of heart contractions (2) determining dissociation between electrical and mechanical heart activity, (3) determining the volume of the heart, (4) determining the origin of sensed intrinsic electrical heart activity signals, (5) recognizing particular arrhythmias (6) disrupting cell membranes for lowering stimulation thresholds, (7) controlling the delivery of a steroid, and (8) obtaining blood flow information.

What is claimed is:  
     
       1. A cardiac rhythm management system comprising: 
       a lead, comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising a first ultrasonic element; and  
       an electronics unit coupled to the proximal end of the lead, the electronics unit comprising:  
       an ultrasound driving circuit; and  
       a signal processing circuit that processes a signal that is based on ultrasound, and in which the signal processing circuit includes an autocapture determination module that determines, using information from the signal that is based on ultrasound, whether a stimulus triggered a resulting heart contraction.  
     
     
       2. The system of  claim 1 , further comprising: 
       an electrode adapted for being associated with a portion of a heart; and  
       a sensing circuit for detecting intrinsic electrical heart activity based on at least one electrogram signal received from the electrode.  
     
     
       3. The system of  claim 2 , in which the signal processing circuit detects occurrences of heart activity using both the ultrasound and the electrogram signal. 
     
     
       4. The system of  claim 1 , further comprising a programmer remote from the electronics unit. 
     
     
       5. A cardiac rhythm management system comprising: 
       an electronics unit, sized and shaped to permit implantation in a human subject, the electronics unit comprising:  
       an ultrasound driving circuit; and  
       means for determining, using information from returned ultrasound, whether an electrical stimulus triggered a resulting heart contraction.  
     
     
       6. The system of  claim 5 , further comprising a lead coupled to the electronics unit, the lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising a first ultrasonic element. 
     
     
       7. The system of  claim 5 , further comprising a lead coupled to the electronics unit, the lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising an electrode for delivering the electrical stimulus. 
     
     
       8. A cardiac rhythm management system comprising: 
       an electronics unit, sized and shaped to permit implantation into a human subject, the electronics unit comprising:  
       an ultrasound driving circuit; and  
       a signal processing circuit that processes a signal that is based on ultrasound, and in which the signal processing circuit includes a slope detection module that provides, using information from the signal that is based on ultrasound, an indication of a strength of a mechanical heart contraction.  
     
     
       9. The system of  claim 8 , further comprising a lead, coupled to the electronics unit, the lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising a first ultrasonic element. 
     
     
       10. A cardiac rhythm management system comprising: 
       an electronics unit, sized and shaped to permit implantation into a human subject, the electronics unit comprising:  
       an ultrasound driving circuit; and  
       means for determining a strength of a mechanical heart contraction using information from a signal that is based on ultrasound.  
     
     
       11. A cardiac rhythm management system comprising: 
       an electronics unit coupled to the proximal end of the lead, the electronics unit sized and shaped to permit implantation into a human subject, the electronics unit comprising:  
       an ultrasound driving circuit; and  
       a signal processing circuit that processes a signal that is based on ultrasound, and in which the signal processing circuit includes an amplitude detection module that detects an amplitude of the signal that is based on ultrasound.  
     
     
       12. The system of  claim 11 , in which the amplitude detection module provides an indication of the volume of a mechanical heart contraction using the detected amplitude of the signal that is based on ultrasound. 
     
     
       13. The system of  claim 11 , further comprising a lead, comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising a first ultrasonic element. 
     
     
       14. A cardiac rhythm management system comprising: 
       an electronics unit, sized and shaped to permit implantation into a human subject, the electronics unit configured to be coupled to an electrode associated with a heart and to an ultrasonic element associated with the heart, the electronics unit comprising:  
       an ultrasound driving circuit;  
       a signal processing circuit that processes a signal that is based on returned ultrasound;  
       a sensing circuit to detect intrinsic electrical heart activity using at least one electrogram signal received from the electrode, and  
       in which the signal processing circuit is configured to detect a dissociation between (1) an occurrence of heart activity detected using the signal that is based on returned ultrasound and (2) an occurrence of heart activity detected using the at least one electrogram signal.  
     
     
       15. The system of  claim 14 , further comprising a lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising the ultrasonic element associated with the heart. 
     
     
       16. The system of  claim 14 , further comprising a lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising the electrode associated with the heart. 
     
     
       17. The system of  claim 14 , further comprising a lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising the electrode associated with the heart and the ultrasonic element associated with the heart. 
     
     
       18. A cardiac rhythm management system comprising: 
       an electronics unit, sized and shaped to permit implantation into a human subject, the electronics unit configured to be coupled to an electrode associated with a heart and to an ultrasonic element associated with the heart, the electronics unit comprising:  
       an ultrasound driving circuit;  
       a sensing circuit to detect intrinsic electrical heart activity using at least one electrogram signal received from the electrode; and  
       means, coupled to the sensing circuit, for detecting any dissociation between (1) an occurrence of heart activity detected using returned ultrasound and (2) an occurrence of heart activity detected using the at least one electrogram signal.  
     
     
       19. The system of  claim 18 , further comprising a lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising the ultrasonic element associated with the heart. 
     
     
       20. The system of  claim 18 , further comprising a lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising the electrode associated with the heart. 
     
     
       21. The system of  claim 18 , further comprising a lead comprising a distal end and a proximal end, the distal end of the lead adapted for being disposed in or about a heart, the distal end of the lead comprising the electrode associated with the heart and the ultrasonic element associated with the heart.